CSS: Style applied to a combination of classes?

Question

I\'m not sure this is possible, but is there a syntax to be used in CSS when you want to style an element based on the combination of classes applied to it?

I understand

Answer 1

$('.bold_green.bold_blue').addClass('something-else');

Or in CSS:

.bold_green.bold_blue { color: pink; }

Notice there's no space between the selectors.